Germanwings has been central to Lufthansa's efforts to compete in the fast-growing budget airline market dominated by Ryanair and Easyjet.

Formed in 2002 from the charter unit of Eurowings, Germanwings became a direct Lufthansa subsidiary in 2009.

Germanwings was kept deliberately small for many years so as not to compete with its parent company. However, Lufthansa then began to invest heavily in the budget carrier to compete with low cost rivals including EasyJet, AirBerlin and TUIfly.

It has operated many short-haul flights for Lufthansa since early 2013. In January, Germanwings completed the takeover of most of Lufthansa's loss-making Europe-only flights.

Only Lufthansa's services for international traffic at Frankfurt and Munich airports were excluded.

Germanwings has about 78 aircraft, serving around 130 European destinations. The budget carrier has around 2,000 employees and last year had about 16 million passengers.

Its fleet comprises Airbus A319, A320 and A330 planes as well as Bombardier CRJ900 NextGen aircraft.

Unions argue that Lufthansa is using Germanwings to unpick long-held agreements on pay and conditions with pilots and cabin staff, and the row has led to months of strikes.

'Excellent safety record'

Lufthansa plans to phase out the Germanwings brand and replace it with Eurowings by autumn this year.

The airline offers flyers three fares: "basic" with no frills, "smart" and "best", which includes free snacks and drinks.

The aeroplane which went down - the A320, which is used as a workhorse by airlines all over the world - has "a formidably good safety record", according to Simon Calder, the travel editor of the Independent.

"Relative to the number of flights in which it's been used, it is one of the safest aircraft in the world," he said.

Lufthansa chief executive Carsten Spohr described the day's events as "a dark day for Lufthansa."

And on the Germanwings and Lufthansa Twitter feeds, the logos were shown in greyscale.